Optics letters最新文献

Adaptive optics (AO) assisted microscopy enables high-quality imaging by correcting instrument- and specimen-induced aberrations, utilizing wavefront shaping devices such as a deformable mirror (DM). For optimal wavefront modulation, it is crucial to position the DM accurately at the conjugate pupil plane and align it symmetrically with the optical axis. However, achieving these requirements can be challenging for researchers lacking a background in AO instrumentation. Here, we propose a simple and practical approach for precisely adjusting the three-dimensional position of the DM using a custom-made bead sample. The experimental results demonstrate the effectiveness of this approach, achieving uniform phase modulation across a total field of view of 60 μm × 60 μm, with a standard deviation of <0.1 λ/2π in the decomposed Zernike coefficients from Z5 to Z25 in Wyant order.

In this Letter, we present an ultra-slow-light metasurface driven by multiple symmetrically protected BIC (SP-BIC) that generates three EIT windows based on three wavelength-stabilized quasi-BIC (QBIC) in two distinct methods. The first EIT is indirectly excited by coupling a QBIC with a leakage mode, resulting in a maximum group delay of 105 ps. The latter two EITs are directly excited by the QBIC, producing group delays as high as 2771 ps, which is 2-3 orders of magnitude larger than previously reported. As a sensor, the metasurface achieves a maximum sensing sensitivity of 415.5 nm/RIU. Furthermore, the first EIT is situated at 1550 nm, where the transverse magnetic (TM) light is fully transmitted, while the transverse electric (TE) light is fully reflected. Metasurface can function as a perfect polarization splitter and filter, and this result can be extended to encompass the entire optical communication spectrum from the O band to U band.

We propose a hybrid fractional Fourier transform (hybrid FrFT) framework for off-axis digital holographic microscopy. This framework combines optical FrFT, implemented via a novel, to the best of our knowledge, three-lens object arm design, with digital FrFT filtering into a unified process. By replacing all FFT operations with FrFT, our approach adaptively minimizes conjugate overlap in spatial frequency distribution and improves the recovery of higher-frequency diffraction components. Both simulations and experimental results reveal significant enhancements in the resolution of amplitude and phase reconstruction while adhering to practical optical design constraints.

The generation of temporal cavity solitons (CSs) in Kerr resonators is well known to lead to the formation of stable frequency combs. In a resonator with pure second-order anomalous dispersion, the soliton's center frequency is pinned to that of the pump field. In this Letter, we consider the operation of CSs in a cavity that possesses a significant component of fourth-order dispersion, which provides a broadband region of parametric gain from which a CS can extract energy. Through the application of a pulsed driving field, temporally desynchronized from the natural roundtrip time of the resonator, we are able to demonstrate the generation of group-velocity-matched CSs, offset in frequency from the pump, and tunable over a ∼1.5 THz range. In addition, we observe a new spectral feature that forms on the opposite side of the pump to the CS that we identify as arising from linear-wave scattering from the CS field.

High-speed rotating objects are widely seen in industrial applications and everyday life. The rotation speed is so high that even minor defects can lead to severe consequences. However, visualizing such small defects online is challenging for conventional imaging, as high-speed rotation results in severe motion blur. In this Letter, we propose a method for visualizing small defects on high-speed rotating objects. The method is based on "time-freezing" single-pixel imaging. It converts a dynamic imaging problem into a static imaging problem by exploiting the repetition of the object's rotation. As such, the method can capture a series of images corresponding to different rotation angles of the target object, even when the object is in operation. Thus, the proposed method enables online defect visualization. To make small defects visible, we propose the use of three equally spaced single-pixel detectors around the object to conduct oblique detection. Such a configuration enhances the contrast of small features. We demonstrate the method by imaging an open hard disk drive that rotates at ~9,700 revolutions per minute. The artificial scratches and fingerprints can be clearly seen in the reconstructed images. We believe that this method holds potential for online non-destructive testing and safety monitoring of various high-speed rotating machinery.

We report on a compact, flash-lamp-pumped Cr-Tm-Ho:YAG (CTH:YAG) master oscillator power amplifier (MOPA) system operating at room temperature. The actively Q-switched oscillator produces 20 ns seed pulses at 2087 nm with an energy of 265 mJ. After a two-stage amplification, the system delivers a maximum output energy of 1.24 J, while maintaining the 20 ns pulse duration. To the best of our knowledge, this work represents the first demonstration of a joule-level, nanosecond CTH:YAG amplifier system, achieving the highest single-pulse energy yet reported from such a configuration. These results establish flash-lamp-pumped CTH:YAG as a viable architecture for developing high-energy, cost-effective 2 µm laser sources.

In this Letter, a technique to enhance the dynamic range (DR) of fiber-optic accelerometers (FOAs) is proposed by incorporating an ultra-weak fiber Bragg grating (UWFBG) into the sensing fiber segment. Demodulation can be performed between any pair of UWFBGs, enabling the sensitivity of the FOA to be adjusted according to application-specific requirements. The detection capability of large-amplitude signals is strengthened through reduced sensitivity. Simultaneously, the capture of weak signals remains guaranteed with the entire sensitivity of FOA. A fiber-optic diaphragm accelerometer (FODA) was constructed for verification, achieving a 14.59 dB improvement in DR. The DR can be further enhanced by optimizing the segmentation of the sensing fiber, demonstrating excellent versatility and stability.

We report on a high-energy, strong-field deep-UV (DUV) pulse system. The system is based on a diode-pumped solid-state laser and employs a distributed face-cooling (DFC) chip-based, sub-nanosecond, joule-class amplifier using Nd:YAG and sapphire, operating at a 20 Hz repetition rate. Using DFC chips enables the realization of joule-class pulse energy at room temperature with minimal thermal lensing and thermal birefringence effects, while allowing the flexible adjustment of the pulse energy and repetition rate. As a result, at a wavelength of 266 nm, the system has achieved a pulse energy of 235 mJ, a repetition rate of 2 Hz, and a sub-nanosecond pulse width of 480 ps. This corresponds to a very high peak power of 0.49 GW, which is comparable to that of excimer lasers and is considered suitable for pulsed laser deposition.

A method is presented to use a fiber-optic device known as a photonic lantern to generate a reconfigurable custom wavefront for a null test of spherical, aspheric, and freeform optical surfaces. By modulating input intensity and phases at single-mode fiber ports, the output light field from the multimode end can be controlled to generate a custom nulling wavefront. Generation of a desired wavefront is demonstrated by simulating a nineteen-port, non-mode-selective photonic lantern. Using a response-matrix inversion approach, a wavefront with an RMS error of 71nm from its target was generated in simulation. A compact form-factor non-interferometric null test for freeform optical surfaces is then simulated to demonstrate utilizing the photonic lantern in a reconfigurable null test of a freeform optic.

We demonstrate spectral broadening and post-compression of high-repetition-rate visible and near-UV pulses from a commercial Yb-pumped optical parametric amplifier (OPA). Second-harmonic pulses from the signal of a 515 nm-pumped OPA (350-500 nm) were broadened via self-phase modulation in a single gas-filled stretched hollow-core fiber to bandwidths supporting sub-30 fs durations. Post-compression using a prism compressor or, for the shortest pulses, chirped mirrors yielded durations as short as 15 fs. The source offers simultaneous tunability in wavelength, bandwidth (Fourier limits 70 fs to sub-10 fs), and pulse duration at repetition rates up to 33 kHz.